CMake config for Mbed


how to use lvgl with new Mbed CMake build system?

I have used lvgl and Mbed already, but with the older python script based build system. Now Mbed is using also CMake as build system and I want to use this.

What LVGL version are you using?

lvgl 8.1-dev

What have you tried so far?

I have added the lvgl subdir to my CMakelist.txt and added the lv_conf.h:


in lv_conf.h I have disabled the examples:


the build starts and compiles the lvgl/src without errors. But then the examples are compiled and throw errors:

[9/116] Building C object lvgl/CMakeFiles/lvgl_examples.dir/examples/assets/img_star.c.obj
FAILED: lvgl/CMakeFiles/lvgl_examples.dir/examples/assets/img_star.c.obj
"C:\PROGRA~2\GNU Arm Embedded Toolchain\10 2020-q4-major\bin\arm-none-eabi-gcc.exe" @lvgl\CMakeFiles\lvgl_examples.dir\examples\assets\img_star.c.obj.rsp -MD -MT lvgl/CMakeFiles/lvgl_examples.dir/examples/assets/img_star.c.obj -MF lvgl\CMakeFiles\lvgl_examples.dir\examples\assets\img_star.c.obj.d -o lvgl/CMakeFiles/lvgl_examples.dir/examples/assets/img_star.c.obj -c D:/Projects/Sn/LocalGit/Mbed6-Projects/lvgl8-ST7735/lvgl/examples/assets/img_star.c
D:/Projects/Sn/LocalGit/Mbed6-Projects/lvgl8-ST7735/lvgl/examples/assets/img_star.c:4:10: fatal error: lvgl/lvgl.h: No such file or directory
    4 | #include "lvgl/lvgl.h"
      |          ^~~~~~~~~~~~~
compilation terminated.

building the examples should be optional, how can this be set in the cmake configuration?
lvgl/lvgl.h is not relative to the examples dir, maybe it can be fixed also by setting the include search path, how is this set in cmake?

I have created a PR for this issue, some files in assets are using the correct …/…/lvgl.h include, some others are using lvgl/lvgl.h which is not found.

It seems to be even better to use the …/lv_examples.h, but I don’t want to break compatibiliy. Are there tests for the different environments like Arduino, Zephyr, ESP IDF and Windows/Linux OS builds?

At the moment, not really. A few of the project repositories have CI on them, however, it only tests that the project itself builds with a specific LVGL commit. The CI doesn’t run in the vice-versa case where LVGL has changed and the project hasn’t.

1 Like

Thanks, I’m still struggling with cmake.
The file(GLOB,…) makes it simple to list all files in the dirs, but there is a note in cmake that does not recommend to do this:

We do not recommend using GLOB to collect a list of source files from your source tree. If no CMakeLists.txt file changes when a source is added or removed then the generated build system cannot know when to ask CMake to regenerate. The CONFIGURE_DEPENDS flag may not work reliably on all generators, or if a new generator is added in the future that cannot support it, projects using it will be stuck. Even if CONFIGURE_DEPENDS works reliably, there is still a cost to perform the check on every rebuild.
file — CMake 3.21.3 Documentation

Its more tedious to list all files manually, but I see this in many other projects that use cmake. Any comments from a cmake user with some experience?

I’ve tested something more and got it running with mbed-os and cmake.

But lvgl uses as default case a static lib build. When I link the static lib to my target, it creates a huge binary, compared to using an interface lib its about factor 2. It looks like the optimization does not remove unused functions from the binary. The lv_conf.h is working, size is changing when I disable/enable options.

Are there any targets using the static lvgl library?